吩噻嗪席夫碱可见光引发剂的合成与性能

Synthesis and Characterization of Phenothiazine-based Schiff Bases as Visible Light Photoinitiators

利用吩噻嗪衍生物的供电子能力及紫外吸收强的特点,通过引入推-拉电子结构,设计并合成了4种Dπ-A型吩噻嗪席夫碱类可见光引发剂,并利用核磁共振氢谱和高分辨质谱表征了其结构.该系列光引发剂在350~450 nm范围内具有摩尔消光系数达10^(4) L·mol^(−1)·cm^(−1)的较强吸收,与商品化Ⅱ型可见光引发剂硫杂蒽酮(ITX)相比,其与405 nm LED光源具有更好的匹配性,与碘鎓盐(Iod)组成的复合光引发体系也具有更高的引发效率和交联基团转化率.通过光解、电子自旋共振波谱和循环伏安(CV)实验证明了吩噻嗪席夫碱可见光引发剂与Iod复合光引发体系的光致电子转移(PET)机理.最后,利用吩噻嗪席夫碱可见光引发剂/碘鎓盐复合引发体系,实现了光致发光器件的数字光处理(DLP)3D打印.

In order to construct photoinitiators with strong molar extinction coefficient in the visible light region,four novel D-π-A type phenothiazine-based derivatives have been designed and synthesized.The structures were characterized by nuclear magnetic resonance and high-resolution mass spectrum.These phenothiazine derivatives,as a strong electron-donating group,can easily undergo photo-induced electron transfer with iodonium salt(Iod),thereby initiating the radical and cationic photopolymerization.Interestingly,the prepared photoinitiators exhibit the charac⁃teristics of charge transfer in the ground and excited states and have the strong molar extinction coefficient of 10^(4) L·mol^(−1)·cm^(−1) in the spectral range of 350—450 nm,and have the red shifts about 50 nm compared with the commer⁃cial photoinitiator 2-isopropylthioxanthone(ITX),well matching the emitting spectra of the popularly used 405 nm LED light source.Theoretical calculations of molecular orbitals also explain the excellent optical properties of photo⁃initiators.The two-component initiating system has faster initiation efficiency and higher conversion rate than that of commercial photoinitiator ITX/Iod for free radical as well as cation photopolymerizations by changing different condi⁃tions of the formulas.The formula with PI(0.2%,molar fraction)and Iod(2%,molar fraction)exhibit the best curing effect.An photoinduced electron transfer(PET)mechanism was established based on steady-state photolysis experi⁃ments,and electron spin resonance spectroscopy experiment which captured the benzene radicals.The free energy changes(ΔGet)were measured by cyclic voltammetry(CV)experiments which proved the possibility of PET mechanism thermodynamically.Under irradiation,APN/Iod undergo the electronic transfer and the formed benzene radicals initiate polymerization of acrylates,and the active species is produced to initiate cationic polymerization of epoxy at the same time.In addition,the printing of fluorescent light-emitting devices was successfully carried out through the technology of Digital Light Processing(DLP)3D printing.